Probing the limits of optical lithography: The fabrication of sub-100nm devices with 193nm wavelength lithography

We discuss the fabrication of a FLASH EEPROM floating gate memory device with a cell size of 0.0896 mu m. The floating gate level utilized an alternating aperture phase shift mask, a binary mask was used to expose the control gate level. Linewidth changes over topography, due to reflectivity variations, was controlled by an inorganic multilayer anti-reflective coating(1). All levels were exposed with a new generation of photoresists developed at Bell Laboratories with ARCH chemicals. Experiments were carried out to give some insight to the behavior of the materials and the viability of optical enhancement techniques. We have found that 193nm lithography with this new family of photoresists is reasonably proficient in the fabrication of devices with design rules of less than half the exposure wavelength.